Deadline for applying is 15/03/2019. Students with Masters in Physics, Maths, Astronomy or related disciplines

The starting date of the studentship is 01/10/2019

Please send (by email) a CV, a motivation letter, the master degree details with marks/subjects and position in the promotion, and, if possible, one reference letter.

The information we have to study a star-planet system comes from photons from this couple. In this context, the description of the atmospheres (stellar and planetary) is of paramount importance, because it is there that the radiation is formed or modified. A realistic modeling taking into account all the richness of the processes at work in the atmosphere (convection, diffusion, radiative transfer, ionization, formation of molecules / dust, refraction) is essential for the correct analysis of current and future observations.

In order to fully understand the stellar and planetary atmosphere, it is crucial to integrate all underlying physics into numerical simulations. Therefore, atmospheric models are essential for much of contemporary astronomy.

It has become possible to produce multidimensional hydrodynamic simulations of the movement of gas coupled with radiation. This 3D approach is necessary for a qualitative and quantitative analysis of both the surface of most stars and the atmospheres of exoplanets.

The aim of the Ph.D. is to achieve a realistic virtual observations of a star-planet system, each component is described by a 3D simulation. This tool will particularly describe an unprecedented level of realism the transit (or the eclipse) of an exoplanet before (or after) its hosting star. This will apply both to the gas giants as well as the terrestrial planets.

The innovation of this work is based on the use of 3D hydrodynamical simulations for the atmosphere of both the host star (Stagger code, Nordlund et al. 2009, Living Reviews in Solar Physics) and the planet (LMDZ, Hourdin et al. 2006, Climate Dynamics, 27) during the transit. The student will work on the analysis of two aspects of simulations and, in particular, on the development of Optim3D (post processing multidimensional radiative transfer code) with the inclusion of diffusion. This physical ingredient is important both for the stellar atmospheres (scattered radiation in the upper layers where the density is low) or planets (scattered light in the optical region). The last step of the work consists in the production of spectra and images at high- resolution as a function of time to fully simulate the exoplanet transit in front of different kinds of stars. The results of such work will have an impact in different areas of astrophysics from exoplanets to stars: eg, reliable study on the impact of stellar activity and full characterization of the atmosphere of the planet during primary and secondary eclipses, brightness and atmospheric dynamics predictions, molecular and abundance of elements detection in the planet's atmosphere, the study of the fog, clouds and albedo of planets.

This work will be important for predicting the phase curves of the JWST and ARIEL space missions and it will be applicable to current observations, for example with ground spectrographs such as SPIrou, CRIRES+ and GIARPS. Moreover, this work will allow the use of Doppler signatures to characterize exoplanets (whether its orbital motion, rotation, or its circulation). Over the next decade, the development of large-aperture telescopes, such as the European Extremely Large Telescope (E-ELT), the Giant Magellan Telescope (GMT) and the Thirty Meter Telescope (TMT) will open new opportunities for studies of extrasolar planets and their atmospheres using the tools developed during the Ph.D. The proposed thesis project will provide a unique radiative transfer code and perfectly consistent for the whole star / planet system. This project falls in a particularly important moment for the preparation to the interpretation of all these observations.